Package arez.promise

Class ObservablePromise<T,E>

java.lang.Object
arez.promise.ObservablePromise<T,E>
Type Parameters:
T - the type of the value that the promise will resolve to.
E - the type of the error if the promise is rejected.
@ArezComponent(requireId=DISABLE) public abstract class ObservablePromise<T,E> extends Object
An observable model that wraps a Promise and exposes observable state that track the state of the promise. The observable exposes the state of the promise as well as the value that it resolves to or the error it was rejected with as observable properties.

A very simple example


 import akasha.Console;
 import akasha.Response;
 import akasha.WindowGlobal;
 import akasha.promise.Promise;
 import arez.Arez;
 import arez.promise.ObservablePromise;
 import com.google.gwt.core.client.EntryPoint;

 public class Example
   implements EntryPoint
 {
   public void onModuleLoad()
   {
     final Promise<Response> fetch = WindowGlobal.fetch( "https://example.com/" );
     final ObservablePromise<Response, Object> observablePromise = ObservablePromise.create( promise );
     Arez.context().observer( () -> Console.log( "Promise Status: " + observablePromise.getState() ) );
   }
 }

  • Method Details

    • create

      @Nonnull public static <T, E> ObservablePromise<T,E> create(@Nonnull akasha.promise.Promise<T> promise)
      Create the observable model that wraps specified promise.
      Type Parameters:
      T - the type of the value that the promise will resolve to.
      E - the type of the error if the promise is rejected.
      Parameters:
      promise - the promise to wrap.
      Returns:
      the ObservablePromise

    • getState

      @Observable @Nonnull public ObservablePromise.State getState()
      Return the promise state.
      Returns:
      the promise state.

    • getValue

      @Observable public T getValue()
      Return the value that the promise was resolved to. This should NOT be called if the state is not ObservablePromise.State.FULFILLED and will result in an invariant failure if invariants are enabled.
      Returns:
      the value that the promise was resolved to.

    • getError

      @Observable public E getError()
      Return the error that the promise was rejected with. This should NOT be called if the state is not ObservablePromise.State.REJECTED and will result in an invariant failure if invariants are enabled.
      Returns:
      the error that the promise was rejected with.